This application claims the priority of German patent document 100 00 550.0, filed Jan. 8, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a system for detecting imminent or occurring vehicle rollovers.
Various methods and systems are known for detecting vehicle rollovers. Most known methods are based on the analysis of different sensors, which directly indicate the rollover, such as rotation rate and acceleration sensors. As a rule, these sensors are arranged in a common housing and are analyzed by a common microprocessor, which processes the detected measured values and emits information obtained therefrom concerning an imminent or occurring rollover to an air bag control unit. The latter, in turn, triggers the corresponding safety systems, such as side air bags, frontal air bags and head air bags or belt tightening devices.
The disadvantage of known systems is their susceptibility to errors in detecting and analysis; as a result, faulty triggering of safety equipment can occur, due to erroneous rollover information, because of a faulty sensor or a defectively operating control device. A faulty algorithm or a faulty data transmission between the rollover sensor system and the air bag triggering unit may lead to a faulty triggering. In this context, repair work on a vehicle while the safety system is active is also problematic. When a rollover sensor is removed from a vehicle, a rotating rate may, for example, be generated which leads to the triggering of the safety system
One object of the invention is to provide a rollover detection system which reliably prevents faulty triggering of safety systems, for example, air bags.
This and other objects and advantages are achieved by the rollover detection system according to the present invention, in which information of rotational wheel speed sensors is also analyzed and used for examining the plausibility of a rollover signal. During a normal drive with a good road adherence, all four rotational wheel speeds are the same, or at least of the same order of magnitude. During cornering, slight differences occur which, however, can be corrected by way of steering angle information. During a beginning rollover, however, first two and, in the course of the rollover, all four wheels will lose contact with the ground. This information is utilized in the present invention. Because of the different points in time of the lifting-off of the wheels and of the different friction conditions of the powered and nonpowered wheels, rotational wheel speeds occur which cannot occur in the normal driving operation. As the result, this information can be utilized to evaluate the plausibility of the rollover signals, and faulty triggering of a safety system can be prevented.
According to various embodiments, it is possible to take into account different rollover sequences in stored algorithms. If a rollover, for example, precedes drastic brake application, when the wheels lift off the road surface, for example, an abrupt braking of the wheels can be observed. This information may also be utilized as additional information and can be processed in the algorithm.
According to a first embodiment of the invention, the signal of at least one rotational speed sensor is used to evaluate the rollover signal. The control unit generates a triggering signal for a safety system first on the basis of the rollover signal, and thereafter takes into account the rotational wheel speed signals and decides on the basis of this plausibility examination whether the safety device should be triggered.
According to a preferred embodiment, rotational wheel speed sensors are provided on all wheels, so that, by way of the analysis of still more information, the current stability condition of the vehicle can be analyzed more precisely.
Vehicle rotation rate and/or acceleration sensors, for example, can be used as rollover sensors, as is generally known.
As mentioned above, when several rotational speed sensors are used, it is advantageous to take into account the information of a steering angle sensor or of another sensor which supplies additional information with respect to cornering. The rotational speed differences occurring during a cornering can then be compensated.
order to detect a defective microprocessor as a fault source, it is also advantageous to provide for all rollover sensors or for each rollover sensor a separate analyzing unit for analyzing the respective rollover signal, and to then connect this analyzing unit with the control unit. As a result, the plausibility information is obtained in a separate component (specifically the control unit) which is independent of the rollover sensor system, and thus of the sensor itself, and of the analyzing unit. An error in the arithmetic-logic unit of the microprocessor itself can therefore be detected and does not lead to a faulty triggering.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.